1. Field of the Invention
The present invention relates to a photonic switching method and a photonic switch utilizing the method.
2. Description of the Related Art
A conventional photonic switch, with input electrical signals input from a plurality of input terminals being switched to a plurality of output terminals, in which the switching operation is performed by utilizing optical signals, converted from the input electrical signals has been disclosed in, for example, an article entitled "System experiments of a 25-Gbit/s ULPHA Switch", Technical Report of The Institute of Electronics Information and Communication Engineers, SSE92-69(1992-10). In the above photonic switch, data portions of packet electrical signals with a bit rate V respectively input from each input terminal are converted by employing a stream of ultrashort optical pulses into ultrafast optical cells with a bit rate nV. Address portions of the packet electrical signals are also converted into optical address signals having a different wave length from that employed to produce the optical cells. The ultrafast optical cells and address signals produced in similar manners at each of the input ports are respectively time-division multiplexed by a star coupler to obtain multiplexed optical signals. These multiplexed optical signals are respectively transferred to a plurality of output ports each constituted of a cell selector, a cell buffer and a cell decoder. Each selector incorporates therein a laser diode (LD) gate switch. A desired ultrafast optical cell can be derived from the multiplexed optical signals by driving the LD gate switch in accordance with the address signal converted into an electrical signal. The derived ultrafast optical cell is controlled in contention by the cell buffer and converted again into an electrical signal with the bit rate V.
As mentioned above, the conventional photonic switch has utilized the technology that the packet electrical signals with the bit rate V input respectively from the input ports are converted into the ultrafast optical cells simply in a manner to be compressed on the time axis, and time-division multiplexed. Therefore, buffering after the cells have been selected at the output ports should be performed with an ultrafast bit rate nV. Furthermore, it requires that the ultrafast optical signal should be converted into a low speed optical signal so as to be easily processed by the successive electrical circuits and that the low speed optical signal should be further processed to be converted into a packet electrical signal.
Also, a desired cell has been selected among the multiplexed optical signals by employing the LD gate switch.
The LD gate switch is, however, operable only in a range of a few tens to a few hundreds GHz and inoperable at a speed of THz, thereby causing difficulty in achieving high capabilities.